JntelUgence and Miscellaneous Articles. SlfS 



of the precipitate, the bases are separated from the piiosphoric acid. 

 I shall subsequently describe in these pages a method by which this 

 may be accomplished without any difficulty. On separating the 

 earthy phosphates by means of ammonia, a small quantity remains 

 dissolved in the filtered liquid, owing to the presence of chloride of 

 ammonium ; consequently upon adding oxalate of ammonia, a pre- 

 cipitate of oxalate of lime is obtained, but its quantity is usually 

 larger than corresponds to the phosphate of lime dissolved by the 

 chloride of ammonium ; consequently a portion of the lime existed 

 as carbonate of lime in the charred mass, or was formed by the de- 

 composition of the sulphate and phosphate of lime by the alkaline 

 carbonates. The liquid filtered from the oxalate of lime indicates, 

 on the addition of a solution of phosphate of soda, the presence of 

 some magnesia. The insoluble earthy salts which separated from the 

 aqueous extract may be examined conjointly with those in the acid 

 extract. 



With respect to the charred mass, which has been exhausted with 

 water and hydrochloric acid, it would be imagined that it could con- 

 tain only silica or silicates undecomposable by dilute hydrochloric 

 acid ; but it yields a very large amount of ash on complete com- 

 bustion, even when the organic substances contain no silica or mere 

 traces. 



I formerly effected the perfect combustion of the cinder in hard 

 glass tubes, in which the mass was heated to redness while a current 

 of oxygen was passed over it ; this plan however has its inconve- 

 niences. If the quantity of organic substance employed is mode- 

 rately large, so much cinder is obtained, that a glass tube, even of 

 large diameter, M'ould require to be filled with it several times to 

 burn it entirely; moreover, the tube is very much acted upon, and 

 rarely stands a second heating. The combustion is in most cases 

 very imperfect, and requires much time if but a slow current of 

 oxygen be passed ; a rapid current is requisite for the combustion 

 to succeed well ; but then a considerable quantity of ash may readily 

 be carried away, especially if it is of a very light nature ; this, it is 

 true, may be partially prevented by passing the gas on its exit 

 through a stratum of Mater, by varying the height of which a dif- 

 ferent pressure may be obtained; but this does not entirely prevent 

 the removal of the ash, and if liie pressure is too great, the glass 

 tube is liable to bulge when strongly heated*. But the greatest 

 disadvantage attending the use of glass tubes is, that it is impossible 

 to collect tiie ashes so as to determine their weight accuratel}'. Fre- 

 quently the ash has undergone sligVt fusion ; it can then only be 

 imperfectly separated from the glass by mechanical means or the 

 use of solvents. The use of thin platinum or silver foil, which is 

 introduced into the glass tube previous to the coal being placed in 

 it, does not entirely remove these serious disadvantages, and gives 

 rise to others. I therefore employ for the combustion of the charred 

 mass a different method, with the results of which I am perfectly 



* The water employed for this purpose contains cyanogen compounds when the 

 charcoal is derived from nitrogenous bodies. 



